Here are some guys hitting targets way smaller than man sized out to 500 yards. Accuracy at 500 yards= 70 percent.
Range accuracy is of course higher than combat accuracy, so let's halve that range and say that a small target can be hit consistently at 250 yards. On the other hand, a man sized target would then extend that range considerably.
But let's be modest and say scaling up to man size would only give 50 more yards. That would give us good accuracy at 300 yards.
However, in Combat Mission, it's nearly impossible to hit anything with a rifle at that range.